1. Field of the Invention
The present invention is generally directed toward systems and methods for digitally printing images onto substrates. More specifically, a digital ink and a catalyst are supplied to an inkjet head, the ink and catalyst being kept separate inside the head. The ink and catalyst are combined after being jetted from the inkjet head.
2. Description of the Prior Art
Digital printing of images onto a medium or substrate presents a number of advantages over conventional printing techniques such as screen printing. Digital printing allows for selective depositing of fine droplets of ink onto the medium in order to form a highly detailed image. Further, digital printing allows for on-demand printing of images without the costly and complex setup that is associated with screen printing.
Conventional inks for use with inkjet printers generally share certain common characteristics. For examples inkjet inks, also called digital inks, generally present low viscosities which facilitate flow of the ink through the very small nozzles of inkjet heads. The low viscosities of digital inks are generally made possible by the presence of a liquid dispersant or solvent in which the solids phase of the ink is dispersed. Once jetted the dispersant or solvent evaporates thereby causing the ink to set or cure on the substrate to which it is applied. Organic solvents, while fast evaporating, are increasingly disfavored due to environmental and workplace regulations limiting release and exposure to such organic vapors. Water-based inks are a more popular alternative to organic solvents, however, water is much less volatile leading to increased drying or curing times.
In some applications, an increased drying time is little more than a nuisance. However, in other applications, increased drying time leads to degradation of the quality of an image as the low viscosity ink can bleed or run on the substrate while the water evaporates. Accelerators can be added to the digital inks to help speed up the curing time, however, such combined systems can be unstable as the ink can prematurely cure or gel inside the inkjet head leading to plugged inkjet nozzles which degrade the quality of images printed using the inkjet head.
The problems with digital inks are particularly pronounced when printing to unconventional substrates such as textiles, glass, synthetic resin materials, and the like. Therefore, a need exists for a printing system for use in connection with a wide variety of substrates that presents the benefits of digital printing without the drawbacks of slow curing times and image degradation that are traditionally associated therewith.